1. Field of the Invention
This invention relates to an ignition position controlling apparatus for a multicylinder internal combustion engine, and more particularly to an apparatus for properly controlling ignition positions of cylinders of a multicylinder internal combustion engine using a microcomputer.
2. Description of the Prior Arts
A control apparatus of such type is generally constructed to apply to a microcomputer a clock pulse generated every fixed angle in synchronism with the rotation of an engine and a cylinder discriminating signal generated at a position predetermined with respect to each cylinder during one rotation of the engine and count a predetermined number of clock pulses on the basis of the position at which each of the cylinder discriminating signals is generated, to thereby obtain an angular data necessary to determine the ignition position of each cylinder. Also, the rotational speed of the engine is detected by measuring time during which a fixed number of clock pulses are generated, and the ignition position of each cylinder is determined depending upon the detected rotational speed.
When an ignition apparatus of the type of interrupting a current is used in an ignition system for a multicylinder internal combustion engine which is adapted to interrupt a current flowing through a primary winding of each of ignition coils at the ignition position, such control apparatus is adapted to determine the position of allowing the flow of a current through the primary winding to be initiated by counting a predetermined number of clock pulses on the basis of the position at which each of cylinder discriminating signals is generated, in which an angle at which the primary current flows is controlled by changing the number of clock pulses to be counted depending upon the rotational speed of the engine.
In view of the foregoing, it will be noted that an ignition position controlling apparatus of such type needs clock pulses generated every fixed rotational angle to provide a data on angular positions and cylinder discriminating signals for providing a data necessary to determine a reference position at which the number of clock pulses with respect to each cylinder starts to be counted.
A conventional control apparatus of such type which has been used for such purpose is constructed to separately generate clock pulses and cylinder discriminating signals by means of an inductor-type signal generator. Therefore, it requires two inductors. The conventional control apparatus has a further disadvantage of requiring a single signal generating means for generating clock pulses and a plurality of signal generating means for generating cylinder discriminating signals in number corresponding to the cylinders, resulting in the signal generator being complicated in construction and oversized. Thus, the conventional control apparatus requires a wide space in order to install the signal generator therein, this resulting in the control apparatus being unsuitable for an engine of a small size such as, for example, an internal engine for a motor bike.